1. Field of Invention
This invention relates to a shut-off valve for a garden sprayer, including oppositely acting fluid chambers and an internal flow passage within the piston.
2. Description of the Prior Art
In the prior art, hand-controlled shut-off valves for garden sprayers and similar apparatus had to compensate for the static and dynamic pressure components exerted by the pressurized fluid controlled thereby. In particular, depending upon the design of the valve, the static force of the pressurized liquid could force the valve from a closed to an open position. This is particularly true in a "push forward on, and pull back off" design. Conversely, the dynamic pressure of the moving liquid could force the valve closed, less open, or more open from a fully or partially open position. The typical solution to this problem was to bias the valve with a spring. However, this added complications in that the Hooke's constant spring must be matched to the static and dynamic pressures of the fluid, the Hooke's constant characteristics of the spring can change over time and with respect to use and exposure. Further, the spring is typically exposed to corrosive chemicals within the pressurized fluid. Any resulting failure in the spring results at least in degraded or inconvenient performance, if not a total failure in function.
Additionally, if a valve in the prior art had a fluid path traversing several interfaces of components of the valve, the valve became susceptible to external leakage and failure.